The invention relates to semiconductor optoelectronic devices with electrically adjustable spectral transfer functions, and especially micro-opto-electro-mechanical (MOEM) devices.
MOEM devices are described in U.S. Pat. Nos. 5,629,951 and 5,771,253 (Chang-Hasnain et al.). To be more precise, they comprise a lower Bragg mirror and an upper Bragg mirror constituted of alternating semiconductor materials with different refractive indices. The two Bragg mirrors are spaced from each other by semiconductor spacers, to define a vertical Fabry-Pérot cavity filled with air. One of the mirrors can be deformed by electrostatic means to vary the thickness of the air cavity and thereby to vary the spectral response of the Fabry-Pérot cavity. The structure can therefore operate as a tunable wavelength filter, a photodetector, or a wavelength tunable laser.
The above devices necessitate conjoint displacement of all the layers of one of the Bragg mirrors, and consequently relatively high electric fields, given the mechanical stiffness of the suspended structure. Moreover, they can provide only one optical signal processing function (tunable filtering), which limits their use in highly integrated optoelectronic components.
An object of the invention is to remedy some or all of the drawbacks previously cited.